A reactor head area assembly is a structure installed on a pressurized water reactor (PWR) head. When a reactor operates normally, the reactor head area assembly performs functions such as cooling of control rod driving apparatuses, forming of a cooling air path, shielding of missile parts, and supporting of the structure with respect to seismic loads. In addition, when refueling is performed, the reactor head area assembly lifts the control rod driving apparatuses and the reactor head at the same time.
As described above, since the reactor head area assembly lifts the control rod driving apparatus and the reactor head when the refueling is performed, research into integrating the reactor head area assembly has been performed in order to reduce the number of structures that should be removed or assembled when a refueling process is performed. Korean Laid-open Patent No. 2000-74957 discloses an integrated head area design of a nuclear reactor.
Referring to FIG. 1, a control rod driving apparatus 6 in a reactor head area assembly is a structure installed on a reactor head 0 in order to insert and withdraw control rods that controls a nuclear reaction speed in a core of the reactor. The control rod driving apparatus 6 is formed in a general tube shape having gaps therein. The control rod moves in an up-and-down direction by the driving shaft in the control rod driving apparatus 6 to control the nuclear reaction speed of the reactor core. A control rod position indicator is a sensor installed on the control rod driving apparatus 6 to sense a position of the control rod. A motor assembly 6a is a structure for driving the control rod.
Operations relating to the control rod driving apparatus 6 are, for example, maintenance of the motor assembly 6a, maintenance of the position director, and a calibration in initial installation of the position director or in re-installation of the position indicator.
FIG. 2 shows an example of a reactor head area assembly according to the conventional art.
The conventional reactor head area assembly includes an upper plenum including cooling fans 1, a shackle 2, and a tripod 3, and a ring type structure that is referred to as a shroud under the upper plenum. In addition, a cable support assembly, a control rod driving apparatus, and a baffle that will be described later are disposed in the shroud.
The cooling fan 1 is installed to cool the control rod driving apparatus, and the shackle 2 and the tripod 3 are used to lift the reactor head area assembly. The shackle 2 is connected to a crane (not shown), and the shackle is also connected to the tripod 3, and thus, the entire reactor head area assembly is lifted when a lifting force is applied upward by the crane.
FIG. 3 is a view illustrating the arrangement of the shroud 4, the baffle 5, and the control rod driving apparatus 6. The portion shown in FIG. 3 is the lowest portion of the reactor head area assembly of FIG. 2. As shown in FIG. 3, a structure, that is, the baffle 5, surrounds the control rod driving apparatus 6, and the shroud 4 surrounds the baffle 5. In FIG. 3, one control rod driving apparatus 6 is disposed in order to clarify the baffle 5 and the shroud 4, however, in actuality a plurality of control rod driving apparatuses 6 are disposed as shown in FIG. 1.
The shroud 4 performs as a cover of the structures therein, and the baffle 5 forms a flow path of air between the shroud 4 and the baffle 5 so that the air drawn by the cooling fan 1 can sufficiently flow therethrough. Therefore, the control rod driving apparatus 6 and the reactor head nozzles can be cooled down easily.
Meanwhile, the shroud 4 is supported by support columns 7 disposed on upper and lower portions of the shroud 4.
The support column 7 is not formed of an H beam that is disposed in a vertical direction, but formed of a plurality of H beams on upper and lower portions of the shroud 4, which are connected to each other. In addition, the shroud 4 is not a shell, but is formed of a plurality of plates. One reactor head area assembly includes three through five layers of shrouds 4, and the number of shroud layers is equal to the number of H beams forming one support column 7. In the reactor head area assembly of FIG. 2, four shroud layers are formed.
The cable support assembly supports cables 10 (shown on FIG. 4) that are connected to the control rod driving apparatus 6 to supply electricity to the control rod driving apparatus 6, or connects signals generated from the position director (not shown) located in the control rod driving apparatus 6 to be output. The cable support assembly is disposed on an upper portion of the control rod driving apparatus 6, and is located on a part denoted as C in FIG. 2. FIG. 4 illustrates a state where the cables 10 are supported by the cable support assembly.
As shown in FIG. 4, the cable support assembly includes a cable support ring beam 8 and a plurality of cable support wires 9. The cable support wires 9 include multiple layers that form grids, and thus, the cable support wires 9 can support the cables 10 with predetermined distances between the cables 10. Meanwhile, both end portions of the cable support wire 9 are fixed on the cable support ring beam 8, and the cable support wires 9 support the cables 10 by penetrating the baffle 5.